Eating disorders that stem from a desire to be thin can be blamed in part on genetics, according to a new US study.
The study, published this week in the International Journal of Eating Disorders, found genetics may make some women more vulnerable to the pressure of being thin.
“We’re all bombarded daily with messages extolling the virtues of being thin, yet intriguingly only some women develop what we term thin ideal internalisation,” said Jessica Suisman, lead author on the study and a researcher at Michigan State University.
The study, which included 300 female twins aged 12-22, measured how much they wanted to look like people from movies, TV and magazines. Identical twins were compared with fraternal twins to establish the role of genetics in thin idealisation.
The heritability of thin idealisation was found to be 43%, meaning almost half of the reason women differ in their idealisation of thinness can be explained by their genetic make-up.
“We’ve known for a long time that there’s a substantial genetic contribution to just about any personality style,” said Tracey Wade, professor of psychology at Flinders University.
“This study helps establish people’s susceptibility to getting caught up in the thin ideal that is presented in the media.”
However John Hopper, director of the Australian Twin Registry, cautioned that the finding of a greater similarity between identical twins than between non-identical in the study could also be due to non-genetic causes.
“Identical twins share environmental and lifestyle factors more than do non-identical twins, especially during the age range of 12-22 years of twins in the current study. Therefore the estimate of “heritability” is likely an over-estimate,” Professor Hoper said.
Dr Wade said there were a range of environmental and genetic contributors that could lead to eating disorders.
“To get a truly environmental variable is rare because our genes play a role in selecting our environments.” For example, she said impulsive people were more likely to suffer adverse life events.
Girls aged between 13 and 15 were most vulnerable to being exposed to environmental and genetic risks that could lead to them developing an eating disorder, Professor Wade said.
“That’s the age when you really want to try and help them not focus on weight and shape, to help them negotiate adverse events, and help them focus on identity rather that what they look like.”
Gary Myers
logged in via LinkedIn
Wondering if being one of identical twins might have a deeper impact on an individuals perception of appearance.
They have someone genetically identical to measure up against, and may also want to, possibly subconsciously, make their appearance more distinctive in regards to their twin.
Isabel Storey
Retired but writing
Could this explain - to some degree - the comfort one feels when as comfortably covered as one's mother and grandmother? Genetic tendency to carry jst that little bit extra in the same places?
ERIC KELLY
retired
Surely our genetic structure determines our reaction to our environment. We should therefore expect twins with identical genetics to react in much the same way to a shared environment while significant differences should be expected between fraternal twins. That, indeed, is what the study found to be the case. The article does not reveal why Professor Hopper thinks that identical twins share environmental and life-style factors more than non-identical twins and I am at a loss to find a reason for so thinking.
Alison Moore
Senior Lecturer in Modern European History, University of Western Sydney
Hopper's cautionary remarks are wise. Twin-studies in genetics often seem to over-reach in their conclusions. They haven't found the gene at all, so it is completely preemptive to insist that this experiment proves the genetic basis of personality.
How do they know that this gene (if it is even just one) is not present in all kinds of people throughout a population without it expressing in that way?
I think what Wade should probably have said is that "we SUSPECT that genes CAN SOMETIMES play a role in selecting our environments."